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Unpredictable water levels for the Atchafalaya River resulting from man's efforts to prevent flooding in South Louisiana lead to an unstable market for Louisiana's annual crawfish production. Empirical models presented show that yields from the basin can be estimated on a monthly basis using bimonthly changes in water level, unemployment rates, and crawfish harvests from ponds. The monthly demand model for basin crawfish yielded a price flexibility of –0.059 and a corresponding price elasticity of –16.94. These empirical results support hypotheses that substitutes for crawfish are available to consumers. Uncertain yields from the basin due to the sort of water level fluctuations documented in this study suggest that investment in this area of the Louisiana crawfish industry will continue to be hampered.  相似文献   
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Skeletochronological analysis provides age estimates, not actual ages, for seaturtles. Unlike age and growth data from captive and headstart turtles, these estimates predict the actual patterns of age and growth in free-living turtles. A moderate-sized sample of 69 Lepidochelys kempii, salvaged from the Atlantic and Gulf coasts of the USA, had straight-line carapace lengths (SCL) of 188–720 mm and age-estimates of 2–15 years. The von Bertalanffy growth model provides the best fit for the age-estimate and size data and predicts maturity between 11 and 16 years, depending upon the body size selected to represent sexual maturity. The logistic growth model suggests later maturity of 13–19 years. Comparison of the Atlantic and Gulf components of the sample suggests a faster growth rate for ridleys in the Gulf of Mexico, although the sizes of the subsamples are too small for this interpretation to be reliable without additional data. Our age and growth estimates indicate that some members of the early cohorts of headstart ridleys are mature and may have nested already.  相似文献   
3.
States are responsible for implementing many key environmental laws enacted during the last 30 years. State level variations in legal, regulatory, and development programs targeted toward the aquaculture industry can affect aquaculture firm decision making, including site location and species selection decisions. This research focused on development and testing of a summated scale measure of state regulatory climate toward finfish aquaculture. Data for the analysis were generated from a national survey of state level finfish aquaculture programs. The final aquaculture regulatory climate scale (ARCScale) ranges from 0–18, with the numerical value of the scale increasing with increases in regulatory stringency. Scale values were computed for each state plus Guam for five categories of finfish: baitfish, ornamentals, commercial foodfish, freshwater gamefish, and marine gamefish. The scale allows direct comparison between states, enabling aquaculture producers to make more informed location, species selection, and business decisions. The scale also provides a means for evaluating changes in state institutional characteristics and regulatory climate over time.  相似文献   
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